When conveying piece goods on roller conveyors it is necessary to provide hesitation or stoppage points or areas in the conveyor path. Conveyed material is held at these points, if required, for example, to insert other conveyed material from a feeder line further ahead on the conveyor path, to collect a number of conveyed material pieces in order to have them continue on their way in a group of a given size, or to effect certain work procedures.
It is known to achieve the stoppage or hesitation of a roller conveyor whose rollers are driven by an endless revolving belt adhering to the rollers by friction. To this end, the stoppage area is equipped with feeler levers or feeler rollers activated by the conveyed material proper and which, when pressed down by the conveyed material, cause the belt to be lifted off a number of rollers in a section preceding the switch mechanism. In this manner, the stoppage point or area remains without any drive, and the pieces of conveyed material are not squeezed together. It is therefore possible to convey delicate material. On the other hand, the extensive mechanism required for the lifting off of the belt and return to the rollers is disadvantageous. This mechanism, consisting of levers, rollers, springs and a large number of moving joints, having a length corresponding to the length of the stoppage area, is complicated and costly, since it must be resistant to disturbances.
A conveyor with a stoppage effect has been proposed which operates without a lever mechanism influencing the drive belt. In this known type of conveyor, the rollers within the stoppage area are constructed eccentrically. The distance between roller axis and drive belt running along the bottom parts of the rollers is such that between a roller and the belt a power is transmitted which is not sufficient to rotate the roller if the "thin" part of the roller is next to the belt. If, in this kind of conveyor, the material stops, the rollers come to rest in the position mentioned. The material resting on top is lifted by the degree of eccentricity while there is slippage between the material and the roller periphery. When the blockage causing stoppage is lifted, at least several rollers turn under the influence of the conveyed material on top, the "thick" part of their periphery touching the belt, and thus start to rotate. The disadvantage in this type of conveyor is that pressure results on the conveyed material, if adjustment of the roller bearings is not performed very carefully with respect to the belt. It is also disadvantageous that the material undergoes strong vibrations when passing the stoppage line. The simplified construction of this known type of conveyor is therefore overcome by considerable disadvantage during operation.
It is the object of this invention to design a conveyor with simple means in such a fashion that the pieces of conveyed material only touch each other lightly during stoppage. This effect is achieved by largely disengaging the rollers from the drive belt without activating moving parts to this end. This is solved in the invention by means of a hesitation or stoppage area roller conveyor whose rollers are rotated by a frictionally engaged endless driven belt. The belt surface facing the rollers has sections of different coefficients of friction where centrically pivoted rollers arranged within the stoppage area are provided with an unbalancing weight, and where the friction between the sections of the belt showing a small frictional coefficient and the rollers is such that the peripheral power transmitted from the belt to the rollers is less than the return momentum of the unbalancing weight, but sufficient to keep those rollers moving with conveyed material which are in rotary motion, and where the friction between the belt sections of greater frictional coefficient and rollers is such that the peripheral power transmitted from the belt to the rollers is greater than the return momentum of the unbalancing weight.
The invention is explained in greater detail by means of an illustrated example shown in the drawings.